Hello Brent, as long as I know, the Earth's speed really has a variation throughout the year, for its orbit being ellliptical, with the Sun in one of the ellipse focuses, it is faster when nearer to the sun (perihelion) and slower when its at maximum distance from it (aphelion).
Both the perihelion and aphelion are upon the ellipse's major axis. As a result, the sun's apparent ecliptical longitude changes a little slower in july than it does in january. Further, as Earth's axis has a declination of ~ 23.5 degrees, that means that the Sun's apparent longitude measured upon the Equator is slightly different of its ecliptical longitude (measured upon the Earth's orbit plan). So, neither is the Sun moving from West to East regulary throughout the year, neither is its movement on the ecliptic equal to that on the Equator - if Sun moves 1 degree with relation to the ecliptic, it may move 58 minutes of arc with relation to the celestial equator. 2011/3/24 Brent <[email protected]> > Hello again; > > I read this at: > http://www.sundialsoc.org.uk/HDSW.htm > > Part 17 > >When we look at the Sun we are observing it from a moving > >platform. It is the varying speed around its elliptical > >orbit and the tilted axis which are responsible for the > >daily variations accounted for by the Equation of Time. > > I'm confused about the varying speed part. > Does the earth actually change speed as it travels around > the sun or is it just the way we perceive it? > > thanks again; > brent > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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